Like many things, this sounds good on paper. To get maximum performance out of this unit, you should use 240v and up to 48 amps-which works out to be 11,520 watts! This will just about take the complete 50amp plug to run-or a big chunk of the generator when running. This is great for a home with 100 or 200 amp service. Granted it can be programmed for less, but don't think it is good for motorhomes.

The main reason for using a regular water heater with a tank, is it is like having a battery. You slowly store the power of hot water in the tank with low electrical draw, and then have instant availability of hot water when you need it. On my bus I have two 10gal straight electric (no coolant loop) water heaters from Home Depot. One is connected to the next with the final water heater wired through my inverter for hot water running down the road. Since installing the water heaters in 1994, I've done nothing to them (except draining them once a year-if I remember). Since a complete 10gal water heater costs less then $300.00 and the heating element is about $25.00, I don't think you could find a cheaper waterheater. When boon docking, I start the generator in the morning to make coffee, turn both water heaters on, and to charge my batteries. Once we've showered, and the water heaters are back up to heat, I turn them off for the rest of the day and have more then enough hot water to get through to the next morning.But-you'll build the bus the way you want-that's why we do them. Good Luck, TomC

They sound good in theory and probably work well, but down the road can and will have one issue or another, along with inverters, toilets, furnaces, etc.. how many pita's you have on your coach can definitely affect enjoyment down the road. I at one time considered them, but a small electric water heater with an engine coolant loop in it, worked for years in our 4104 with no issues except for replacing the electric element because I had drained water system and forgot to turn off the power circuit breaker. Duh!

In a past bus, we had a propane instant water heater. It worked well. Since is was propane, it was good for dry camping too. It had low water flow, which some people would mind but was okay with me. We now have a 10 gallon electric heater and use it much the same way the Tom does. It is a reasonable set up also.

... a small electric water heater with an engine coolant loop in it, worked for years in our 4104 ...

Yeah, I really like the coolant loop in my water heater. It's like "free hot water" if you are driving more than 20 minutes. (And I'd agree that it adds a small amount of complication but it's a very small added amount of complication.)

The new Attwood on demand heaters for RV's work good I just installed one so far so good it doesn't seem to be bad on propane seems to be more efficient on propane use than the older type Attwood with a tank

Ive had one in my bus for over 25 years with no problems. Yea, it uses lots of propane -for a few seconds-- or minutes when having a shower but you can have hot water for as long as your water and propane hold out. And it takes up minimum space.

There was a great discussion about this over at BNO a while back and George and Sean (not me...but rather the one and only Sean Welsh) made some great points about going tankless http://www.busnut.com/bbs/messages/233/71751.htmlDefinitely worth the read if you are contemplating. I did a bit of research on this and George and Sean were spot on with their comments.